Metallurgical process



sept. 3o, 1924. 1,509,947

W. E. GREENAWALT METALLURGICAL PROCESS Original Filed July 22, 192] I N VEA/'TOR4 @Mmfm Patented Sept. 30, 1924.

lUNlTED STATES PATENT OFFlCE.

WILLIAM E. GREENAWALT, 0F DENVER, COLQBADO.

METALLURGICAL PROGSS.

Application filed July 22, 1921 Serial No. 486,817, RenewedAugust 28, 1923.

To all whom t may concern:

e it known that I, WILLIAM E. GREEN- AWALT, a citizen of the United States, residing in the city and county of Denver and State of Colorado, have invented certain new and useful Improvements in -Metallurgical Processes, of which the following is a specification.

The process refers more particularly to the treatment of the complex ores which are common in the western part of the United States, Canada, and Mexico. These compleX ores usually contain recoverable values in lead, copper, gold, silver, and zinc. The zinc frequently occurs in considerable amounts, usually associated with the lead. The association of the minerals of these metals is usually so intimate that it is diiicult to make a satisfactory separation of them by any mechanical process, such as concentration or otatiom although a satisfactory separationV from the gangue can usually be made.

The zinc, in galena concentrate, is a great detriment, and usually involves a penalty if the concentrate is shipped to a smelter, and the zinc content of the concentrate has no commercial value. Similarly, the copper in the concentrate cannot be separated entirely from either the zinc or the lead by any mechanical process, although usually a partial separation may be made. The gold and silver is usually associated with the lead, and to some extent with the copper. The copper is usually associated With the iron.

It will be seen, therefore, that these complex ores offer a very dilicult problem for their economic treatment, because'a treatment which may be eminently adapted to the ores of one metal, may be totally inadequate for the ores of the other metals. Even direct smelting of these ores is eX- pensive and inadequate. If lead smelting is attempted, the copper and the zinc give trouble, and the zinc is lost. is obtained as a matte or speiss, which needs further strenuous treatment. If copper smelting is attempted, the lead recovery is inadequate, the zinc gives*1 trouble, and is lost, and the copper and precious metals are only concentrated into a matte, which is only a step in their final separation and recovery in metallic form.

My present process contemplates the re The copper covery of all the metals in the metallic form by a combination of pyrometallurgy and hydrometallurgy, so inter-related that the different steps and operations form a complete Whole.

It has been stated that the separation of the minerals from the gangue can usually be effectively accomplished, and that the principal difficulty is in the separation of the various metals from one another, altho there is no difficulty in making at least a partial separation.

The preferred method of operating the process will now be described. Reference may be had to the accompanying drawing, which represents a diagrammatic flow sheet.

The ore, as'it comes'from the mine, is mechanically concentrated in the mill, into three different products. Une concentrate is preferably a high grade galeria, containing only a small percentage of zinc, and possibly a ve small amount of copper. This will be known as the lead concentrate, Another concentrate is high in zinc, containing more or less lead and some copper, although the lead and copper are preferably, but not necessarily, kept quite low. This will be known as the zinc concentrate. Another concentrate is very high in iron, as pyrites, and contains most of the copper, most of the gold, some silver and some lead. It is a sort of middling product. This concentrate will be known as the copper concentrate. Both the lead and zinc concentrates may contain gold and silver. The treatment of the dilferent concentrates will now be described.

lead concentrata-The lead concentrate is given a partial roast to prepare it for sintering, since the direct sintering of unadulterated galena is diliicult and unsatisfactory. ln order to prepare the lead concentrate for elective smelting, the partially roasted material is mixed with about 10% water, and sintered into large chunks, with the simultaneous elimination of all but a small percentage of sulphur. `A satisfactory 'apparatus and process for sintering is described in` Patents, No. 1,348,407, August 3. 1920, and No. 1,348,408, August 3, 1920. The sintered material, with fuel and iiuX, is then charged into the smelting furnace, where the lead and precious metals arerecovered as lead bullion. The small amount of impurities'` in the sinter are `easily slagged .posited copper.

off'. The small amount of copper in the galena concentrate will appear as matte or speiss, which is pulverized and added to the copper concentrate. The small amount of zinc in the lead concentrate goes with the slag, The smelting of the lead concentrate, under these conditions, is an exceedingly simple matter, and very little fuel or flux will be required. The smelting will amount to little more than the mere reduction of the galena, or sintered product resulting from the galena., Under these conditions a comparatively small smelting furnace will have a comparatively large output.

Copper concentrata-The copper concentrate is roasted to make as much as possible of the copper soluble in Water and as high a percentage as possible soluble in dilute acid. There is no difficulty il. making from to 7 5 per cent of the copper soluble in Water and from 90 to 98 per cent soluble in dilute acid. The pulverized matte or speiss from the smelting furnace is added to the copper concentrate going to the copper roasting furnace. As much as 8O per cent of the copper in a low grade matte can be made soluble in Water by mixing it With pyritic ore or concentrate and roasting under suitable conditions. A very large percentage of the copper content of the roasted copper concentrate can therefore be made soluble in Water, and the remainder can readily be extracted to a high percentage with dilute acid. If the leached copper is deposited electrolytically, thek process can be made self sustaining in acid. Suitable process and apparatus for this purpose will be found described in various patents issued to me on this subject matter, among Which may be mentioned, No. 1,357,495 November 2, 1920, and No. 1,353,995, September 28, 1920.

The copper concentrate as it issues from the roasting furnace is char ed into a leaching vat Where a dilute solution of sulphuric acid is applied to it.4 The resulting copper solution, containing considerable amounts of zinc and some salts of iron, is flowed into the electrclytic copper cells Where the copper is deposited as the electrolytic metal with the simultaneous regeneration of lacid and ferrie salts. The zinc in the electrolyte remains unaffected; it may act beneficially in the deposition of the copper by restraining the solvent action of the ferrie salts on the de- The electrolyzed and regenerated solution is returned to the roasted copper concentrate, and the cycle continued until the solution becomes foul, or unfit, for copper leaching and electrolysis, and charged with salts rof iron and salts of zinc, and very likely containing other impurities. The foul electrolyzed copper solution, containing as high a zinc content as possible, is then passed on to the zinc department and applied to the z1nc concentrate as will be described later.

The foul copper solution, instead of being chemically precipitated and Wasted as is now the universal practice, is used in the extraction tof the zinc.

The residue may contain considerable lead and some gold and silver. The treatment of the residue Will, depend largely on the valuable content after copper leaching. It will be practically free from copper and Zinc, and if it does not contain other valuable metals it may be removed from the leaching tank and Wasted. Ordinarily the residue may contain lead and may contain small amounts of gold and silver. After copper roasting and leaching much of the gold and silver is recoverable by amalgamation, so that the residue may be passed over amalgamators and the precious metals sufficiently recovered, and at Very small expense, when the precious metal content is so small as not to Warrant a more expensive, and possibly a more efiicient, treatment. The lead may be recovered in various Ways. In roasting and leaching most of the lead Will have been converted into the sulphate. The lead in the residue, Whatever its chemical composition, may be separated from the residual gangue by some simple method of concentration, such as gravity concentration, flotation, or hyposulphite leaching may be used to advantage in some cases Where mechanical methods are not applicable, since lead sulphate is readily soluble in hyposulphite. If flotation is applicable, the lead sulphate may be sulphidized preliminarily to flotation, with some sulphidizing agent, such as hydrogen sulphide or sodium sulphide. Some precious metal values Will also be concentrated with the lead. Whatever the form of the lead concentrate from the copper residue, it is transferred to the regular galena mixture, preparatory to sintering, and sintered With it, and thus finds its Way to the lead smelting. or reduction, furnace, where the lead and precious metal values are recovered with` and the same as, the lead and pnecious metal values in the galena concentrate. As much or as little of the copper leach residue may be added to the lead concentrate for the purpose of sintering. If no clean separation can be made between the Worthless gangue and the residual lead and precious metal values in the copper leach residue, all the residue may be added to the'lead concentrate for sintering, and this mixing will sufficiently reduce the sulphur content of the lead concentrate so that. the mixture will sinter easily and completely. If, on the other hand, a partial separation can be made, either by fiotation or otherwise by retaining a large portion of the gangue with the concentrate of the copper leach residue, this low grade concentrate can be added to the lead concentrate and the barren residue Wasted. Again, if the copper leach residue can be successfully treated to concentrate all the residual values, then this concentrate is added to the lead concentrate, and the residual gangue of the copper leach residue may be Wasted. The details of operating the process Will, necessarily, depend largely on the nature of the ore treated and on the judgment and discretion of the operator.

Zinc concentrata-The zinc concentrate is roasted to makeas much as possible of the zinc soluble in Water or dilute acid. The roasted zinc concentrate is then charged into the leaching tank and the zinc extracted with an acid solution, preferably a solution of sulphuric acid. The zinc sulphate solution is then purified and electrolyzed to obtain the electrolytic zinc and regenerate the combined acid. The regenerated acid is then again returned to the zinc concentrate to dissolve more zinc. In this application of the zinc solution to the zinc concentrate, I prefer to use the foul solution from the copper leaching, since this solution is presumed to be already heavily charged with zinc sulphate and also contains some free acid. Instead, therefore, of applying the ordinary acid solution to the zinc concentrate, I use the foul solution from the copper leaching and electrolysis, and then by the addition of considerable free acid, saturate the solution with zinc from the roasted zinc concentrate. The solution is then purified as usual, but in the purification, hydrogen sulphide is first applied to the impure saturated zinc solution, Which precipitates the copper as lthe sulphide, as also any of the other metal values which the solution may contain and which are precipitatedl With that reagent. 'In this Way both the small amount of copper remaining from the copper leaching and electrolysis and the small amount which Will inevitably be extracted under the conditions in the leaching of the zinc concentrate, Will be recovered as the sulphide and ultimately as the electrolytic copper.

The amount of zinc residue will be small, since the zinc concentrate is assumed to be of high grade, and almost all of the zinc will have gone into solution and deposited as the electrolytic metal. What small residue remains, consisting largely of lead and possibly a very small amount of iron and copper, is transferred to the mixer of the sintering plant, the same as the lead residue from the copper leaching, Where the lead and possibly some precious metal values are recovered as described, by sintering and furnace reduction. Precious metal contained free in the zinc residue may be recovered by amalgamation if desired. Y

rlhe copper sulphide, obtained from the zinc solutions', is transferred to the copper leaching system, Where it may be used, either raw or roasted, to reduce the ferrie salts and neutralize free acid, and Where the copper of the precipitate is converted into the electrolytic metal, as described more particularly in my Patents, No. 1,340,826, May 18, 1920, and No. 1,357495, Nov. 2, 1920.

In the operation of the process it,Will usually be desirable to transfer all thelead and precious metal residues from the copper and zinc concentrate to the mixer of the sintering furnace. In this Way all the lead and precious metal values Will be easily and cheaply concentrated into lead bullion. The sintering of the lead and precious metal residues with -the galena is a very simple matter, and offers an easy Way of effectively collecting the precious metal values into one end product.

The roasting of the copper concentrate Will require some care to make as much as possible of the copper soluble in water and as much as possible of the remainder soluble in dilute acid. Ordinarily there will be no diiculty in getting from 50% to 75% of the copper soluble in Water, under the conditions of this process. With the copper effectively removed from the copper concentrate, the treatment of the copper leach residues offers no particular diliculty.

The process has been described as if most of the commonly occurring metals, such as copper, lead, zinc, gold and silver, Were in the ore. It may frequently happen that only some of these metals are present in commercial amounts. The process is easily modified to suit the varying conditions, as will be evident to .any one skilled in the art of metallurgy.- The amount of zinc in the copper solution, when it is found advisable to transfer it to the roasted zinc concentrate, 'is necessarily ay variable quantity, and will have to be determined by the operator. It will depend largely on the relative amounts of copper and zinc in the respective concentrates, and the transfer will naturally be made When the operator thinks the solution is suiciently charged with zinc to get the best average results both in the copper deposition and zinc leaching, and this can only be determined by experiment and eX- perience with each particular ore. The idea, however, naturally Would be to get as'much zinc as practicable in the solution, from cpper leaching, and then bring it to saturation, or the desired percentage, in the zinc leaching.

I claim:

1. A metallurgical process comprising concentrating ores containing copper and zinc into a concentrate relatively high' in copper and low in zinc and a concentrate relatively high in zinc and low in copper, separately roasting the copper and the zinc concentrates, repeatedly applying an acid solution to the roasted copper concentrate to extract the copper and the Zinc, repeatedly precipitating the copper from the resulting copper leach Solution, and then When the solution becomes charged with zinc from copper leaching applying the solution to the roasted zinc concentrate.

2. A metallurgical process comprising concentrating ores containing copper and Zinc into a concentrate relatively high in copper and loW in zinc and a concentrate relatively high inl zinc and low in copper, sep arately roasting the copper and zinc concentrates, repeatedly applying a solution to the roasted copper concentrate to extract the copper and the zinc, repeatedly precipitating the copper from the resulting copper leach solution, and then when the solution becomes charged with zinc from copper leaching applying the solution to the roasted zinc concentrate to extract the zinc and the copper, precipitating the copper from the resulting zine solution, applying the resulting precipitated copper from the Zinc solution to a succeeding copper leach solution, and electrolyzing the purified resulting solution highly charged with zinc from the zinc leaching to deposit the zinc.

3. A metallurgical process comprising treating ores of copper containing zinc with an acid solution to extract the copper and some of the zinc, precipitating the copper, repeating the cycle until thei copper solution becomes charged With zinc, and then applying the copper leach solution containing zinc to av zinc ore to extract the zinc.

4. A metallurgical process comprising treating ores of copper containing Zinc with anpacid solution to extract the copper and some of the zinc, precipitating the copper with the simultaneous regeneration of acid, repeating the cycle until the copper leach solution becomes sufliciently charged with zinc, and then applying the copper leach solution containing zinc to a zinc ore to extract the zine. y

5. A metallurgical process comprising treating ores of copper containing zinc with an acid solution containing salts of iron to extract the copper and`som ofthe zinc, electrolyzing the copper solution containing zinc to deposit the co per with the lsimultaneous regeneration oi) acid and ferrie salt, returning the solution to the ore and repeating the cycle until the solution becomes snliiciently charged with zinc, then applying a portion of the copper leach solution to ores of zinc containing copper, precipitating the copper in the zinc leachv solution, vand applying the precipitated copper from the zinc solution to the copper electrolyte.

6. A metallurgical process comprising treating ores of copper containing zinc with an acid solution toiextract the copper and the zinc, electrolyzing the'copper solution containing zinc to deposit the copper and regenerate the solution, returning the regenerated solution to the ore and repeating the cycle until the copper solution becomes suficiently charged with zinc, then'applying a portion of the foul copper leach solutions to ores of zinc containing copper, precipitating the copper from the resulting zinc solution, and electrolyzing the purified Zinc solution to obtain the electrolytic zinc.

7. A metallurgical process comprising roasting a material relatively high in copper and relatively low in zinc and roasting a material relatively high in zinc and relatively lov7 in v copper, leaching the copper material to extract the copper With the simultaneous extraction of the zinc, precipitating the copper from the copper leach solution, returning the copper solution to the ore and continuing the copper leaching until the copper solution becomes suiiicient ly charged with zinc, then applying the leach solution containing some copper to the roasted zinc material containing some copper, precipitating the copper from the resulting zine solution, and electrolyzing the resulting purified zinc solution to obtain the electrolytic zinc.

8. A process of treating complex ores containing lead, copper, and zinc, comprising roasting a copper concentrate containing lead and zinc, leaching the roasted material to extract the copper and the zinc, electrolyzing the resulting copper solution containing zinc to deposit the copper and regener ate the solution, returning the regenerated solution to the ore and repeating the cycle until the solution becomes sufficiently charged With zinc, then applying the copper leach solution to a zinc ore containing copper and lead to extract the zinc, precipitate ing the copper from the resulting zinc solution and applying the precipitated copper to the copper electrolyte, and recovering the lead from the leach residues practically free from copper and zinc.

9. A process of treating complex ores containing lead, copper, zinc, and precious metals, comprising forming a concentrate high in galena, a concentrate relatively high in copper and relatively low in lead and zinc, and a concentrate relatively high in zinc and relatively low in copper and lead, smelting the galena concentrate into metallic lead containing a portion of the precious metals, leaching the copper concentrate to extract the copper and zinc, precipitating the copper from the solution with the simultaneous regeneration of the solution, returning the regenerated solution to the copper concentrate and repeatin the cycle until the solution vbecomes su ciently charged With zinc, then applying the copper leach solution to the zinc concentrate to extract the zinc and copper from the zinc concentrate, and recovering the' lead from the leach residues and smelting it with the galena concentrate to recover the metallic lead and residual precious metals.

10. A process of treating complex ores containing lead, copper, zinc and other metals comprising forming a concentrate high in galena and relatively free from other metals and a concentrate containing the other metals and relatively low in galena, roasting and smelting the galena to metallic lead, roastin and leachin the concentrate containing t e other meta s to extract the metals therefrom Which are soluble in the leach solution, then treating the leach residue to obtain a lead concentrate relatively free from other metals, and then smelting the lead concentrate so obtained With the original galena to recover the metallic lead and residual metals not soluble in the leach solution.

11. A process of treating complex ores comprising forming a concentrate high in galena and a concentrate high in iron and containing most of the copper and some lead and precious metals, sintering the galena concentrate, roasting the copper concentrate, leaching the roasted copper concentrate to extract the copper and other soluble metals,

treating the copper leach residue to concentrate the lead and precious metals contained therein, and mixing the residue concentrate with the galena concentrate, sintering the mixture and smelting the resulting mixture to recover the lead and the precious metals.

f2. A process of treating complex ores comprising forming a concentrate high in galena and a concentrate containing the residual metals with some galena, oxidizing and sintering the galena concentrate, leaching the roasted residual metal concentrate to extract the metals soluble in the leach solution thus leaving a residue containing lead, mixing the lead residue with the galena concentrate, sintering the mixture, and then smelting'v the resulting sinter to recover the lead and the metals not soluble in the leach solution.

13. A metallurgical process of treating complex ores containing galenavcomprising crushin the ore, separating the crushed ore into a iigh grade galena, a tailing, and a middling product containing the -residual values, roastin the middling product, leaching the roaste material to extract the metal values, precipitating the metals from the leach solutions, and adding the precipitate to the galena concentrate and smelting thel mixture to obtain the metal values in a lead bullion.

14;. A metallurgical process of treating complex ores containing alena comprising separatingthe ore into a igh grade galena and a resldual product containing zinc and other metal values, roasting the i residual product, leaching the residual product to extract the zinc and other metals soluble in the zinc leach solution, then treating the zinc leach residues to separate the remaining metal values from the relatively barren gangue, and then smelting the concentrated metal values so obtained with the galena concentrate to obtain the metals in the form of lead bullion.

15. A metallurgical process of treating complex ores containing lead, copper, and other metals, comprising separating the 4ore into a high grade galena concentrate and a residual product containing the copper and other metal values, roasting the residual product, leaching the roasted material to extract the larger portion of the copper and other metal values soluble in the copper leach solution, then mixing the resulting leach residue still containing a small amount of copper and the residual metal values with the galena concentrate and smelting the mixture to obtain the major portion of the metal values in the form of lead bullion and a minor portion asV copper matte or speiss, crushing the' resulting copper matte and adding it to the residual product resulting from the ore concentration in the cyclic operation of the process.

16. A metallurgical process of treating complex ores containing lead, zinc, and other metal values comprising roasting the ore, leaching the roasted ore to extract the zinc and other metals soluble in the zinc leach solution, concentrating the resulting leach residue to get a product high in lead, then smelting the concentrate from the leach residue to obtain the remaining metal values in the form of lead bullion.

17. A metallurgical process of treating complex ores containing lead and other metals comprising crushing the ore, separating the ore into a high grade galena concentrate, a tailing, and a middling product containing the residual values, roasting the middling product, leaching the roasted material to extract the metals soluble in the leach solution, then mixing the leach residue Withthe galena or lead concentrate, sintering the mixture, and then smelting the sintered material to obtain the metals in a lead bullion.

l 18. A process of treating complex ores containing lead, copper, and precious metals comprising, treating ythe ore to forma concentrate high in lead and a concentrate containing the copper and residual values in lead and the precious metals, roasting the copper concentrate, leaching the roasted .concentrate to extract the copper, then mixing the roasted and leached copper residue or a portion thereof with the lead concentrate, sintering the mixture, and then smelting the sinter to recover the lead and precious metals in a lead |bullion.

19. A process of treating complex ores containing copper and other metals comprising, roasting the ore, leaching the roasted ore to extract a portion of the copper and other metals soluble in the leachisolution, and the-n when the soluble metals in the ore are sufficiently extracted smelting the residue to obtain the remaining metal values into a lead bullion and copper matte, vcrushing the copper matte, and adding the crushed matte to a new ore charge.

20. A process of treating complex ores containing lead, copper, zinc, and precious metals comprising, roasting the ore, leaching the roasted ore with an acid solution to extract copper and zinc, electrolyzing the resulting solution to deposit the copper and regenerate acid, returning the regenerated acid solution to the ore and repeating the' cycle until the solution becomes sufliciently charged With zinc, then purifying the solution and electrolyzing it to deposit the zinc, smelting the leach residue, and recovering the lead and precious met-als as a lead bullion.

21. A process of treating complex ores containing lead, copper, zinc,and precious metals comprising, roasting the ore, leaching the roasted ore with an acid solution to extract copper and zinc, electrolyzing the resulting copper-zinc solution to deposit the copper and regenerate acid, returning-the regenerated acid solution of the ore and repeating the cycle until the solution becomes sufficiently Kcharged with Zinc, then purifying the solution and recovering the zinc therefrom, smelting the leach residue, and recovering the lead and precious metals as a lead bullion.

22. A process of treating complex ores containing copper, lead, zinc, and precious metals comprising, roasting the ore, leaching the roasted ore with an acid solution to ex* tract copper and zinc, electrolyzing the resulting solution to deposit the copper, then purifying the solution and treating it to recover the zinc, smelting the leach residue to recover the lead and precious metals as lead bullion and the residual copper ascopper matte, crushing the matte and adding the crushed matte to a new ore charge. 23. A process of treating complex copper lore containing zinc comprising, roasting the ore, leaching the ore with an acid solution to extract copper and zinc, electrolyzing the resulting solution to deposit the copper and regenerate acid, returning the regenerated acid solution to the ore and repeating the cycle until the solution becomes sufiiciently charged with zinc, then purifying the solue tion and electrolyzing it to deposit the zinc.

24. A process of treating copper ores containing other metals comprising, roasting the ore, leaching the roasted ore with an acid solution to extract copper and other metals, electrolyzing the resulting solution to deposit copper and regenerate acid, returning the regenerated acid solution to the ore and repeating the cycle until the solution becomes suiiiciently enriched with other metals to make their recovery dcsirable, chemically precipitating the copper remaining in the solution after the copper electrolysis, reducing the acidity of the solution, purifying the solution, and then electrolyzing the solution to deposit other metals therefrom.

25. A process of treating copper ores containing other metals comprising, roasting the ore, leaching the roasted ore with an acid solution to extract copper and other desired metals, electrolyzing the resulting solution to deposit copper and regenerate acid, returning the regenerated acid solution to the ore and repeating the cycle until the solution becomes sufiiciently enriched in the other desired metals, then treating the solution with a material containing the dcsired metals in relatively concentrated form, purifying the solution, and recovering the desired metals from the purifed solution.

26. A process of treating copper ores containing other metals comprising, roasting the ore, leaching' the roasted ore with an acid solution to extract copper and other desired metals, electrolyzing the resulting solution to deposit copper and regenerate acid, returning the regenerated acid solution to the ore and repeating the cycle until the solution kbecomes sufiiciently enriched in the other desired metals to facilitate their recovery, then treating the solution with a material containing the desired metals in relatively concentrated form, purifying the solution, and then electrolyzing the solution to recover the' other desired metals.

' WILLIAM E. GREENAVVALT. 

